This invention relates to a multi-pole circuit interrupter having a first pole unit provided with an operating mechanism, a second pole unit provided with no operating mechanism but having an alarm switch, and a partition wall between the first and the second pole units.
A conventional circuit interrupter to which the present invention pertains will be described in conjuction with FIGS. 1 to 4. FIG. 1 is a plan view of a conventional multi-pole circuit interrupter; FIG. 2 is an enlarged cross sectional view taken along line II--II of FIG. 1; FIG. 3 is a partial enlarged sectional view taken alog line III--III of FIG. 1; and FIG. 4 is a partial enlarged view of FIG. 3 illustrating the TRIP position.
In these figures, the circuit interrupter comprises an electrically insulating housing 1 composed of a base 1a and a cover 1b. The insulating housing 1 is divided by two partition walls 1c into three compartments in order to house therein respective pole units of the multi-pole circuit interrupter. In the illustrated embodiment, the circuit interrupter has a centrally disposed, first pole unit 1A which is provided with an operating mechanism 20, and two second pole units 1B having no operating mechanism and, each provided with an alarm switch 30 (FIG. 3) for detecting the tripping of the circuit interrupter. In each pole unit, a stationary source side conductor 2 is mounted on the base 1a and has a stationary contact 3 secured thereon. Mounted in the housing 1 is an automatic trip unit 4 which comprises a trip unit of a thermally responsive electromagnetic type or an electronic type. A stationary load side conductor 5 is electrically connected to the automatic trip unit 4. A movable contact 6 is secured to a movable member 7 which is electrically connected to the automatic trip unit 4 through a flexible conductor 8 and a connector 9. The movable member 7 is supported by a contact arm assembly 10 comprising a first contact arm 10a connected to the operating mechanism 20 which will be described in more detail later, and a second contact arm 10b on which the movable member 7 is pivotally supported by a first pin 11. The first contact arm 10a of each pole unit is also connected to a cross bar 13 for the simultaneous movement of the pole units. The first contact arm 10a and the second contact arm 10b are independently pivotally supported within the housing by a pivot pin 12. The first contact arm 10a has formed therein a first guide hole 14 extending substantially in a direction of movement thereof. The second contact arm 10b has formed therein a second elongated guide hole 15 extending in a direction of extension thereof. A sliding pin 16 extends through the first and the second guide holes 14 and 15 to limit the relative pivotal movement between the first and the second contact arms 10a and 10b. The sliding pin 16 is biased toward a free end portion of the contact arm 10b by a tension spring mounted between the sliding pin 16 and the first pin 11 pivotally connecting the movable member 7 to the second contact arm 10b. In order to provide a contact biasing force between the movable and the stationary contacts 6 and 3, a contact pressure spring 18 is disposed between the movable member 7 and the second contact arm 10b. As is well known, an arc extinguisher 23 is provided in order to extinguish the arc generated between the contacts when they separate. In the first pole provided with an operating mechanism, an operating handle 19 is connected to an operating mechanism 20 comprising a releasable cradle 20a having a stop pin 21 and a pair of toggle links 20b and 20c connected between the cradle 20a and the first contact arm 10a by pivot pins 22a and 22b. In order to releasably latch the cradle 20a of the operating mechanism 20, a latch 24 is pivotally supported by a pin 25. The latch 24 is engaged by a latch lever 27 which in turn is engaged by a trip rod 26 of the automatic trip unit 4.
In order to transmit the movement of the cradle 20a of the operating mechanism 20 (FIGS. 1 and 2) in the first pole unit 1A to the alarm switch 30 (FIGS. 1 and 3) disposed in the second pole unit 1B through the partition wall 1c, and opening 28 is formed in the partition wall 1c so as to allow an actuator pin 29 (FIG. 1) extending from an actuator 31 which is pivotally mounted by a pin 32 within the second pole 1B to actuate the alarm switch 30. It is seen that the actuator 31 is a substantially U-shaped member having two leg portions 31a and 31b bent from an elongated plate as seen in FIG. 1, but its leg portions 31a and 31b are different in length and define an acute angle between them when viewed from the side as seen in FIG. 3. The actuator 31 is biased by a torsion spring (not shown) to rotate clockwise about the pin 32 as shown by an arrow 35 in FIG. 3. The shorter leg 31a has the actuator pin 29 which extends through the opening 28 and is engageable with the latch end of the cradle 20a, and the longer leg 31b has an end engageable with the alarm switch 30 for the actuation thereof.
When the first pole unit 1A of the circuit interrupter is in the ON position shown in FIGS. 1 and 2, an electric current flows from the source side stationary conductor 2 to the load side stationary conductor 5 through the stationary contact 3, the movable contact 6, the movable member 7, the flexible conductor 8, the connector 9 and the automatic trip unit 4 in the named order. When the second pole unit 1B of the circuit interrupter is in the ON position shown in FIGS. 1 and 3, an electric current flows from the source side stationary conductor 2 to the load side stationary conductor 5 through the stationary contact 3, the movable contact 6, the movable member 7, the flexible conductor 8 and the connector 9 in the named order.
When the operating handle 19 is moved into the OFF position as shown by an arrow 33 of FIG. 2, the contact arm assembly 10 is lifted by the operating mechanism 20 so that the movable contact 6 together with the movable member 7 is moved away from the stationary contact 3 to separate the contacts 3 and 6. At this time, since the sliding pin 16 is positioned in the recessed portion 14a of the guide hole 14 due to the biasing function of the tension spring 17, the second contact arm 10b is rotated about the pivot pin 12 into the opening direction by the operating mechanism 20 together with the first contact arm 10a until it abuts against the stop pin 21. Since the first contact arms 10a of the pole units are rigidly connected to each other by a cross bar 13, three pole units open simultaneously.
In the ON position shown in FIGS. 1 and 2, when an overload current flows through the circuit interrupter, the automatic trip unit 4 is actuated to release the cradle 20a of the operating mechanism 20 to allow it to rotate in a direction of arrow 25 of FIG. 2. Then, the toggle links 20b and 20c of the operating mechanism 20 rotate the contact arm assembly 10 in the clockwise direction in the figure to separate the movable contact 6 from the stationary contact 3, thereby interrupting the overload current. This is the socalled tripped position. During this operation, since the sliding pin 16 is positioned within the recessed portion 14a of the guidehole 14 due to the tension spring 17, the second contact arm 10b is rotated clockwise about the pivot shaft 12 by the operating mechanism 20 together with the first contact arm 10a until it abuts against the stopper pin 21. This movement of the first contact arm 10a of the first pole unit 1A is transmitted to the first contact arm 10a in the second pole unit 1B through the cross bar 13, so that the contact arm assembly 10 of the second pole unit 1B is also moved into an open position as shown in FIG. 4.
As soon as the cradle 20a is released and rotated during contact opening, the actuator pin 29 is released from the engagement by the cradle 29 so as to allow it to move upwardly, and the actuator 31 shown in FIG. 3 rotates about the pin 32 as shown by the arrow 35. Then, the longer leg 31b of the actuator 31 moves away from the alarm switch 30 as shown in FIG. 4, whereby the alarm switch 30 detects the fact that the operating mechanism of the circuit interrupter is in a tripped position and generates an alarm indicative of the tripping of the circuit interrupter.
When a large current such as a short-circuit current flows through the circuit interrupter in the ON position shown in FIGS. 1 to 3, an electromagnetic repulsive force generated between the stationary conductor 2 and the movable member 7 causes the movable member 7 to immediately separate from the stationary conductor 2. At this time, since the operating mechanism 20 does not allow the first contact arm 10a to be actuated because it is not actuated, the second contact arm 10b rotates clockwise about the shaft 12 by moving the sliding pin 16 against the spring force of the tension spring 17 from the recessed portion 14a along the guide hole 14 until it abuts against the end portion 14b of the guide hole 14. The electromagnetic repulsive force generates very quickly upon the occurence of a short-circuit current and therefore contact separation is achieved before the operating mechanism 4 is actuated, providing a high current limiting capability.
With the conventional multi-pole circuit interrupter as above described, the movement of the cradle 19 is transmitted to the alarm switch 30 by the upward movement of the actuator pin 29 extending through the partition wall 1c. Therefore, the opening 28 for allowing the movement of the actuator pin 29 must be an elongted hole as shown in FIGS. 2 to 4. Thus, the opening 28 has a relatively large area, communicating the compartments through the relatively large opening, so that the electrical insulation between the compartments provided by the partition wall 1c is degraded.